<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <link rel="stylesheet" href="css/test2.css">
    <title>抽奖</title>
</head>
<body>
    <div class="content">
        <div class="top">
            抽奖活动
        </div>
        <div class="body">
            <table>
                <tr>
                    <th>百度</th>
                    <th>腾讯</th>
                    <th>阿里</th>
                    <th>京东</th>
                    <th>华为</th>
                </tr>
                <tr>
                    <th>滴滴</th>
                    <th>蚂蚁金服</th>
                    <th>乐视</th>
                    <th>中国电网</th>
                    <th>中石化</th>
                </tr>
                <tr>
                    <th>美团</th>
                    <th>乐视</th>
                    <th>小米</th>
                    <th>网易</th>
                    <th>酷我</th>
                </tr>
                <tr>
                    <th>爱奇艺</th>
                    <th>盛大</th>
                    <th>短文学</th>
                    <th>浅墨诗韵</th>
                    <th>浪子一秋</th>
                </tr>
            </table>
        </div>
        <div class="bottom">
            <input type="button" name="" id="button" class="button" value="开始" onclick="toStart(this)">
        </div>
    </div>
</body>
<script type="text/javascript">
    var timer;
    var button = document.querySelector("#button");
    function toStart() {
        // 启动定时器
        if (timer == undefined) {
            timer = setInterval(changeStyle, 100);
            button.setAttribute("value", "停止");
        } else {
            clearInterval(timer);
            timer = undefined;
            button.setAttribute("value", "开始");
        }
    }
    // 改变样式
    var a, b;
    function changeStyle() {
        var tb = document.querySelector("table");
        console.log(a);
        if (a != undefined) {
            tb.rows[a].cells[b].style.backgroundColor = "white";
        }
        // 获取要操作的元素
        a = parseInt(Math.random() * 4);
        b = parseInt(Math.random() * 5);
        // console.log(a);
        var col = tb.rows[a].cells[b];
        col.style.backgroundColor = "red";
    }
</script>
</html>